The English words good and well are often confused by native and non-native speakers of English - this is a good lesson that will put you well on your way to understanding the difference.
Good
Good is an adjective, which means that it modifies nouns.
- This is a good movie
- What a good idea!
- You speak good English
Good can be used with popular verbs (that is, verbs which express a state of being, such as to be, to seem, and to appear), but it is still an adjective modifying a noun, not a verb.
- This movie is good
- His ideas are good
- Your English is good
Well
Well is an adverb, which means that it modifies verbs, adjectives, and other adverbs.
- Did the movie do well at the box office`
- It was a well-defined idea
- You speak English well
Well can be used as an adjective to mean "in good health."
- You look well
- I don't feel well
The Bottom Line
The confusion between good and well comes from their similar meanings, and a general confusion between adjectives and adverbs. Take a moment to think about what the word is modifying: if it's a verb, you'd do well to use well; otherwise, the good choice is good.